7/26/2019 Vortex Meter Installation and Straight Length Requirements

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1. VORTEXMETERINSTALLATIONANDSTRAIGHT

LENGTHREQUIREMENTS

Like most flow devices, a Vortex flow meter requires a well developed andsymmetrical flow velocity profile, free from any distortions or swirls if it is to give

good accuracy and repeatability. To achieve good accuracy and repeatability it is

standard practice to place the meter some distance from sources of turbulence.Common sources of turbulence include pumps, valves, changes in line direction i.e.

bends!, changes in line si"e etc.

#ost manufacturers provide the user with minimum distances for their particular

products. These distances, refered to as straight lenghts, are indicated in $ipe%iameters %!. &or example, '( % means place the flow meter ten times the pipe)s

inside diameter away from the source of turbulence. *ecause turbulence bothupstream and downstream can reduce accuracy, manufacturesrs provide straight

length requirements for up and downstream of the meter.

%ifferent manufacturers claim differing requirements, with fewer straight lengthsbeing marketed as an advantage for the end user.

+deally the flow transmitter should be sited with as many upstream and downstream

straight pipe lengths as possible, preferably more than recommended by themanufacturer, but definately not less.

btaining the necessary straight lengths can be difficult, especially in compact plants.

Therefore it is worth remembering that Vortex meters can be installed vertically,hori"ontally, or at any angle, as long as they are kept flooded.

+f you are compensating for pressure and temperature then allow - to pipe

diameters between the meter and downstream pressure taps, and thermowells shouldbe small and located / to 0 % downstream of the meter.

1s a general rule of thumb straight lengths should be about the same as that required

for an orifice installation with a beta ratio of (.2 3 see the table below

4ource of Turbulence 5pstream %iameters %ownstream %iameters

Line reduces in si"e '/ % / %

Line increases in si"e -/ % / %

4ingle 6(7 bend -( % / %

Two 6(7 bends

in same plane-( % / %

Two 6(7 bends

in different planes( % / %

&ully open valve -/ % / %